1. Field of the Invention
The present invention relates to an image reading apparatus, and more particularly to an image reading apparatus that reduces of show-through.
2. Description of the Related Art
In an image reading apparatus, such as an apparatus disclosed in Japanese Laid-open Patent Publication No. 02-242390, a plate-like surface mirror is arranged on the back of a medium to be read (referred to as “medium” in Japanese Laid-open Patent Publication No. 02-242390). The apparatus disclosed in above patent is directed to read an image on a thin medium to be read clearly.
In the technique disclosed in Japanese Laid-open Patent Publication No. 02-242390, light diffused by the medium to be read or by each unit of the apparatus other than light irradiated from a light source is guided to the surface mirror. When the diffused light is transmitted through the medium to be read and guided to an image sensor, the image sensor also reads an image on the back of the medium to be read. Therefore, in this technique, there is a possibility that the image on the back of the medium to be read comes out on a surface (a read surface) of the medium to be read is read, that is, there is a possibility of so-called show-through.